The roller bearings used in the steering systems or on the wheel hub assemblies of vehicles comprise an outer ring, which may be flanged in the case of bearings intended for equipping a wheel hub assembly and an inner pair of flanked rings, arranged coaxially with respect to a common axis of relative rotation with the outer ring and rotatable with respect to the outer ring for the insertion of two bands of rolling bodies.
The rolling bodies, generally balls, are fitted between the outer and inner rings of the roller bearing with the insertion of a unit formed by the rolling bodies and by a cage for containing the rolling bodies inside the outer ring, and then inserting the inner rings into the “pack” consisting of the rolling bodies retained by the associated cage and already fitted inside the outer ring. However, it is also necessary to guarantee that the rings, in particular the inner rings, do not escape, for example during transport or in any case before final assembly. For this purpose at least the inner rings must be provided with integral axial shoulder means that prevent them from accidentally escaping from the “pack” consisting of the rolling bodies retained by the associated cage and already fitted into the outer ring.
According to several known solutions, such means of shouldering are composed of elastic means of retention (“clip rings”) or other means of locking that are fitted integrally between the inner rings after their insertion, or that are rendered integral by the rolling body containment cage. According to other known solutions, on the other hand, a roller bearing is made that has a shoulder obtained integrally in one piece with each inner ring and the assembly of the rolling bodies takes place by “snap-in” forcing, profiting from the elasticity of the materials with which the inner and outer rings and rolling bodies are made, generally steel, and above all profiting from a specially studied geometry of the shoulder obtained integral with each inner ring.
A dual solution is also known in which the shoulder is made on the outer ring, on each axial end of the same, and the “pack” of balls is first fitted on an inner ring, with the creation of a unit which is then inserted from one side of the outer ring and that then receives the second inner ring with the associated balls from the other side.
In any case, the shoulder creates an annular sub-square that keeps the rolling bodies in position after their insertion and renders the roller bearing “self-retaining”, but which must be got over, “jumped” in effect, during the insertion phase. A similar solution is known, for example from U.S. Pat. No. 7,648,283 and from US2012/0148181.
Nevertheless, it has been found that during insertion of the rolling bodies on the inner rings (or on the outer ring), the rolling bodies can be subject to relatively high localized stresses that can damage them, with the consequent generation of noise in use; furthermore, the friction in use of the known roller bearings is relatively high, with consequent undesired energy consumption and especially with undesired heating of the roller bearing.